Resilient mounting for microphones



H. w. DARR RESILIENT MOUNTING FOR MICROPHONES Filed oct. 15, 1944 March 11,- 1947.

lPatented Mar. 11', 1947 UNITI-:D STATES PATENT foi-FICE RESLIENT MOUNTNG FOR MICROPHONES Harold W. Barr, Minneapolis, Minn., assignor '-to The Maico Company, Incorporated, Minneapolis, Minn., a corporation of Minnesota Application October 13, 1944, Serial No. '558,587

1i clan-ns. (ci. ivo-14e) 'l This .invention yrelates to a mounting for a H microphone and while the invention might have :application in many devices, it particularly is designed for the Amounting of a microphone in a hearing aid. v

One of 'the objections Vto hearing aids is What is known `:as case noise. :This is caused by the fact that the `casing of the instrument is vibrated as the personwearingitimoves. The casingrubs on the clothing of the wearer and lis sometimes vcontracted vby other objects causing vibrations in the casing, which vibrations are transmitted to the microphone ofthe -'instrument creating all `sorts'o'f lpeculiar and confusing sounds. Infsome `designs the sounds so created'may be so powerful that the amplilier of the hearing 'aid may be .seriously overloaded Vand any speech sounds com- .ing through fat 'the `same time will be very'badl-y distorted due to the overloaded condition created by the .adventitious sounds. In `considering a `solution of 'therabove objection the main problem is to eliminate orto attenuate the transmission of the casing vibrations to. the microphone. It is `necessary to have a good acoustical seal between the iront of the ymicrophone and the casting, otherwise sounds produced inside of the cas'- .ing by the vibration thereof will leak into the microphone, thus increasing case noise. It is also -necessary'that themicrophone be rmly mounted so that it cannot move about lor flutter inthe casing if the instrument is shaken with considerable `force. If the microphone is not so mounted a sudden impact will throw the microphone into a fluttering condition-for two 'or three seconds 'andthe powerful 'low frequencyairwaves so produced impinging on the microphone diaphragm will generate very peculiar sounds in the instrumerit. It 'is .also very desirable to have the micro- .phone mounted'for easy removal.

It is an object of this invention to provide a microphone mounting of simple and eiilcie-nt construction and one which will substantially eliminate case noise.

It is another object Vof the invention to provide 'a mounting for a microphone in the casing of a hearing Said 'or other vinstrument by vmeans of which the microphone `will be very firmly but resiliently held in position and which will sub- Astantially'eliminate1case noise.

Itis also an object fof theinvention to provide a mounting for a microphone within a casing Acomprising .a member Vof Vresilient material engaging the casing and supporting the microphone.' said member being so constructed and `arranged'thatit will have great compliance .under small vibrations and decreasing compliance under heavier vibrations.

It is still further anobject of the invention :to provide a mounting structure for .a lmicrophone in a casing comprisinga member of resilient material. disposed in .the casing and engaging the same, said member `supporting the microphone and having a plurality of portions 'engaged by the casing, said portions normally being engaged over a `small area, said area however, increasing as said portions are compressed.

It is more speciiically lan object of lthe invention to provide amounting for aimicrophone car ried in `a casing comprising a'member of `resilient material supporting 'said'microphone and having a plurality of portions adapted `to be engaged by said casing, some `of which portions are normally out of engagement with the 'casing but adapted to be brought linto such engagement upon the occurrence of sufcient stress'between said member and casing.

These and other objects and advantages of 'the invention will be fully set forth in the following description made vin connection with the accom panying drawings in which like reference vcharacters refer to similar parts throughout the several views and in which:

Fig. l is a plan view of the rear side of front casing with microphone mounted therein;

Fig. 2 is a vertical section taken on line 2-2 of Fig. 1 as indicated by the arrows; Fig. 3 Vis ya partial vertical section taken on Iline 3.3 of Fig. '1 las indicated by the arrows; Fig. 4 is a viewvv .partly in :si'de' elevation :and partly in radial section of a-supporting member used; and

Fig. 5 is a View in side elevation of a. modiiied form 'of supporting member.

Referring to the drawings aportion of a casing I0 is shown in `plan in Fig. lythe `same having e, troni-wall 10a and having a side yor surrounding angeflllb directly rearwardly. Lugs Iclextend inwardly from flange .I0b and Lare apertured or tapped to `receive `securing screws for holding a cover 10h on :casing I0. The front side lua of the casing .has an opening lud therethrough, the same `havinga rabb'eted portion or shallow recess lue extending thereabout. Opening 10d may be inthe form of slots formed in a grill. Casing 0 has an inwardly externlingflange Ill illustrated Vas of substantially cylindrical form. A member ll of resilient. material is fitted snugly within the flange If, the same having `a hat side engaging a ,layer of grilllcloth vvI2 which maybe made -ofsomefcloselyfiwoven fabric Said clot'h l2 v`vis disposed against the inner side of casing I and extends across the opening lod. Member II which is shown as annular in form, has a plurality of peripheral projections IIb illustrated as equally spaced and of semi-cylindrical form, which engage the inner Wall of flange If. Said flange is thus engaged by member II at spaced points. A microphone I3 is provided, the same being shown as having a flange I3a projecting outwardly from its periphery. The diaphragm I3b of the microphone overlies flange I3a and preferably has its edge portion secured thereto in any suitable manner as by soldering or welding. Electrical conductors I3c are shown as leading from the inner side of microphone I3. Member II which is substantially in the form of a ring, has a slot IIa at its inner side in which the iiange I3a and diaphragm I3b secured thereto are disposed and in which they are snugly fitted. Microphone I3 is thus supported in the member or ring II. The projections IIb of member II are continued at one side of said member and form in effect pillars shown as cylindrical in form, and it will be noted that said projections or pillars have their flat terminal ends in different planes. Preferably alternate ones of said projections IIb will have their terminal surfaces in the same plane. A securing member I4 forming a removable part of casing I0 is provided, the same being formed of thin resilient sheet material and being substantially in the form of a at ring. Said ring surrounds the body of the microphone but is spaced slightly therefrom at its inner side. Said ring is provided with a plurality of circumferentially spaced slots I4a and portions of metal from these slots are bent downwardly to form tongues or resilient prongs I 4b, the terminal ends of which project outwardly as shown at I4c, and are disposed in a slot I0g extending` about the inner side of flange I 0f. The inner flat surface of ring I4 normally engages the terminal surfaces of the longer projections IIb. Member or ring II is thus normally under some compression. `The ring I4 is so constructed that it can be placed over the microphone I3 into engagement with the projections IIb and the circumferentially spaced prongs or tongues I4b then pressed or snapped into position in flange If. The microphone I3 is thus mounted for convenient and quick removal by merely prying the ring I4 from its securing position,

In operation the microphone will be supported as described and will be very iirmly held in position in the member or ring I I. The microphone is also indirectly held by the ring I-4 which engages and holds in place the member II. Any vibrations occurring in the casing I0 will .be communicated to the ring I4 which will in turn transmit them to the projections IIb of member I I. There is a comparatively small area of these projections IIb engaged by the ring and the compliance or yielding effect of these projections will be quite large. Any small vibrations therefore, will be taken up or absorbed by the yielding or resilient action of the projections IIb. Should greater vibrations or shocks occur in casing I 0, the projections IIb normally in contact `with ring I4 will be so compressed that said ring will move into position to engage the other projections IIb. The vibrations will thus be transmitted to a greater number of projections IIb and the compliance of member II and its projections IIb will be reduced. The vibrations will be effectively dampened by the resilient action ofthe projections IIb... The projections IIb 4 could of course, be arranged to be progressively engaged by the ring I4.

In Fig. 5 a different form of resilient member is shown comprising a member I1 which is likewise in the form of a ring and of the same construction as member II except that instead of the cylindrical projections having at terminal surfaces, projections I'Ia are provided having semi-cylindrical peripheries at the sides of ring I'I but with the portions projecting at one side of member II having converging sides with small or pointed terminal ends. The ring Id will engage the tops of the projections I 'Ia and it will be seen that there will be quite a small area normally in contact with ring I4. When slight vibrations occur in the casing I0 the compliance or yielding effect of the projections I Ia will be quite large and said vibrations will be quickly absorbed by the yielding or resilient effect of said projections. The greater the vibrations in the casing, the greater will'be the compression of projections I'Ia and the greater will be the area of contact between ring I4 and said projections. It will thus be seen that in both of the modifications shown there is a greater area of contact between the casing and member II during heavy vibrations or shocks than during very light vibrations. The vibrations are thus effectively absorbed and case noise is substantially eliminated.

The aim of the mounting is of course, to secure an acoustical low pass filter between the microphone and the casing. The more effective the attenuation of the iilter, the less vibration of the casing is transmitted to themicrophone. Two of the main factors in such a filtering action are the mass of the microphone casing and the compliance of theresilient mounting ring. Ideally the mass of the microphone should be as great as possible. This of course, cannot be achieved because the hearing aid must be made as light as possible. Also ideally the compliance of the mounting ring should be as great as possible. This also cannot be accomplished because the microphone would then move about or flutter. In the present structure the rubber or body of member Il is stressed only in compression. It thus cannot fail mechanically and there is no danger of the microphone falling or moving about in the casing. The ring II has been so constructed as to oifer a very small area of contact to resist small vibrations butto oier a larger area of contact to greater vibrations.Y Two opposing objectives have thus been achieved. It could be said that the compliance or yielding effect of the yielding member II varies inversely with the applied force or force of the vibrations. This inverse function is not necessarily a linear function but could be made in various ways so as to be non-linear. y

From the above description it will be seen'that I have provided a very simple, compact and efficient mounting for a microphone.v The microphone is mounted so that, it can be easilypremoved and yet it is so mounted that it is rmly supported in the casing and cannot move about or flutter therein. The structure is `also such that any vibrations of the casing are not transmitted to the microphone and case noise is thus eliminated. The device has been amply demonstrated in actual practice, found to be very successful and eiiioient and is being commercially made.

It will of course, be'understood that various changes may be made in the form, details, ar-

rangement and proportions of the parts Without departing from the scope of applicants invention, which generally stated, consists in a device.

capable of carrying out the objects above set forth, in the parts and combinations of parts disclosed and defined in the appended claims.

What is claimed is:

l. A mounting structure for a microphone having in combination, a casing, a microphone within said casing, a resilient member supported by said casing and supporting said microphone, said member having a small area normally engaged by said casing and a larger area engaged by said casing upon vibration of said casing.

2. A mounting structure for a microphone having in combination, a rigid casing, a microphone within said casing, a resilient member supported. by said casing and supporting said microphone, said member having a small area normally engaged by said casing and having another area normally out of engagement with said casing but constructed and arranged to engage said casing under stress.

3. A mounting structure for a microphone having in combination, a casing, a microphone Within said casing, a resilient member supported by said casing and supporting said microphone, said resilient member having a plurality of portions normally engaged by said casing and a plurality of portions normally out of contact with said casing but disposed adjacent thereto and adapted to be engaged by said casing upon sufcient compression of said rst mentioned portions.

4. A mounting structure for a microphone having in combination, a casing, a microphone with.. in said casing, a resilient member supported by said casing and supporting said microphone, said resilient member having a portion With a small area normally engaged by said casing and constructed and arranged to have a greater area engaged by said casing upon compression of said portion.

5. A mounting structure for a microphone hava plurality of spaced portions, some of which are normally engaged by a pant of said casing and a part of which ,are only engaged during vibration of said casing,

7. A mounting structure for a microphone having in combination, a casing, a member of resilient material having one side thereof engaging said casing, a microphone supported by said member,

said member having a portion of comparatively small area at its opposite side engaged by said casing, said member having an additional portion at said opposite side normally adjacent but out of Contact with said casing but adapted to be engaged by said casing upon vibration thereof.

8. A mounting structure for a microphone having in combination, a casing, a ring of resilient material engaging said casing, a microphone supported by said ring, said ring having spaced projections at its opposite side and means supported by said casing and engaging a small area of said projections but constructed and arranged to engage a larger area upon vibration of said casing.

9. A mounting structure for a microphone having in combination, a casing, a member of resilient material having one side engaging said casing, a microphone supported by said member and held against lateral movement thereby and a member removably engaging said casing and engaging a substantially opposite side of said first mentioned member holding the same in compression, said first mentioned member having a small area normally engaged by said second member and having a larger area adapted to be engaged by said seeond mem-ber upon compression of said resilient member.

10. A mounting structure for a microphone having in combination, a casing, a microphone, resilient means engaging said casing and disposed about said microphone, said microphone having a. portion supported in said resilient means, said resilient means additionally engaging said casing over a small area of said means, said second member being formed as a ring of sheet material having prongs, said flange having a recess in Which said prongs engage.

l1. A mounting structure for a microphone having in combination, a casing having a flange projecting at one side and provided with a groove, a microphone, a ring of resilient material disposed about said microphone, said microphone having a projecting portion disposed in said ring, said ring engaging said side, a ring of thin resilient material having spaced prongs projecting substantially at right angles therefrom having terminal portions adapted to engage in said groove, said ring overlying and engaging said first mentioned ring.

HAROLD W. DARE..

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENT Number Name Date 2,327,136 Shapiro Aug. 1'?, 1943 1,983,937 Guedon Dec. 11, 1934 1,124,636 Miller Jan. 12, 1915 2,169,806 Lean Aug. 15, 1939 OTHER REFERENCES A. P. C. application of Pohls, Ser. No. 378,894, published May 18, 1943. 

